A point charge q1 = 3.45 nC is located on the x-axis at x = 2.25 m, and a second point charge q2 = -6.60 nC is on the y-axis at y = 1.30 m. What is the electric field at the origin due to these charges?

a. 9.81 N/C
b. 12.45 N/C
c. 6.28 N/C
d. 15.72 N/C